Non-rechargeable cells

used for: remotes, alarms and other small devices that don't need a lot of power and, are only used for a short amount of time.

the half equations for this are not reverseable because it is not practical to reverse them in a battery.

batteries can be made to run backwards but this can cause it to leak or explode. The zinc casing becomes thinner as it is oxidised in this way.

also the ammonium ions would produce hydrogen gas which would escape making it impossible for the ammonia to reform by reversing the reactions.

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Rechargeable cells

Rechargeable cells use reverseable reactions

They are found in lots of devices like: phones, laptops and cars.

Lead-acid cells are used in car batteries. They normally consist of 6 cells connected in series. Each cell is made up of a lead anode and a lead(IV)dioxide cathode immersed in a sulfuric acid elctrolyte. Both electrodes end up coated lead(II)sulfate.

Other types of rechargeable battery are NiCad(nickel-cadmium) and L ion(lithium ion).

To recharge these batteries a current is supplied to force electrons to flow in the opposite direction around the circuit and reverse the reactions.

This is possible because none of the substances in a rechargeable battery escape or are used up.

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Pros and cons of non-rechargeable cells

Cost: non-rechargeable batteries are cheaper for the short-term but in the long-term rechargeable batteries are cheaper as they only require one purchase.

Lifetime: non-rechargeable batteries last longer but have to be thrown away at the end where rechargeable batteries do not.

Power: rechargeable batteries can supply more power than non-rechargeable batteries, so are used more in power hungry devices like laptops and phones.

Use of resources and waste: more non-rechargeable batteries are produced which uses more resources and creates more waste than rechargeable batteries. Both types can be recycled but they instead often end up in landfills.

Toxicity: non-rechargeables are less likely to contain toxic lead and cadmium(might have some mercury though), so they're less hazardous in landfills if they leak.

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Fuel cells

In most cells the chemicals that generate electricity are congtained in the electrodes and the electrolyte that form the cell.

In a fuel cell the chemcials are stored seperately and used only when electricity is needed.

An example is a hydrogen-oxygen fuel cell, which can be used to power electric vehicles.

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Pros and cons of fuel cells

Pros

They don't need electrical recharging, as long as hydrogen and oxygen are supplied the cell will continue to produce electricity.

Only waste product is water, no harmful chemicals or gaseous emissions from the cell as a bi-product.

Cons

Energy is needed to produce a supply of hydrogen and oxygen from electrolysis from the waste water.

The initial energy for hydrolysis is mostly likely obtained from fossil fuels so the process is not usually carbon-neutral.